Fluid powered diaphragm pumps are known. However, in currently available fluid powered diaphragm pumps, the stroke of the pump is fixed and defined by the construction of the pump. When it becomes necessary to adjust or change the stroke of a diaphragm pump, the pump must be disassembled and modified.
It is often necessary to change the stroke of a diaphragm pump. For example, if it is desired to transfer a defined volume such as 525 gallons with a diaphragm pump that has fixed displacement of 0.325 gallons per stroke, the required 525 gallon volume cannot be accurately displaced because the strokes required is not a whole number (525/0.325=1615.385). In the above example, setting the stroke count at 1615 results in a displacement of too little liquid; setting the stroke count at 1616 results in the displacement of too much liquid. Thus, to produce the desired volume of 525 gallons in 1615 strokes, the pump displacement must be adjusted to 0.32508 (0.3250774) gallons per stroke. In order to accomplish this in a currently available fluid powered diaphragm pump, the pump must be disassembled and modified.
One such way to modify the pump is to disassemble the pump and thicken or use a thicker inner diaphragm plate. The inner diaphragm plate effects the length of the stroke because in many currently available designs, it is the inner diaphragm plate that contacts the pilot valve actuator. Thus, by using a thicker inner diaphragm plate, the pump stroke is shortened; by using a thinner diaphragm plate, the pump stroke is lengthened. However, this strategy is extremely inconvenient as it requires a major disassembly of the pump.
Further, when changing the pump stroke for the first time, the operator must often undergo a cumbersome trial and error process. That is, the pump must be disassembled, the thickness of the inner diaphragm plate changed, the pump reassembled, and tested so that the pump stroke can be accurately measured. Often, the pump must fine tuned by adding or subtracting the shim. Thus, the disassembly and reassembly of the pump in order to achieve the desired stroke displacement require a substantial amount of labor and down time.
The demand for adjusting the stroke length of diaphragm pumps is increasing. For example, a diaphragm pump may be used to pump ink to a printing head in a separate diaphragm pump used to scavenge the ink that is not consumed in the printing process. In order to simplify the installation and operation of the system, it may be required that both pumps be the same basic construction and run from a common controlled air supply. Further, it is typical to require the scavenger pump to pump more than the ink supply pump to prevent an overflow situation. Accordingly, in this situation, it would be convenient to easily shorten the stroke length of the supply pump while using the optimum or maximum flow rate for the scavenger pump.
Another application involves the use of a dual ported design with a single diaphragm pump. Specifically, each pump discharge chamber may be equipped with its own suction and discharge porting. Effectively, two single acting pumps are created from one diaphragm pump assembly. When this design is employed, it is often necessary to modify the stroke length of one or both of the diaphragm chambers. Specifically, if one side of the pump acts as a supply pump and the other side acts as a scavenger pump, it would be necessary to increase the thickness of the inner diaphragm plate of the ink supply pump side in order to ensure that the scavenger pump side is pumping at a greater capacity than the ink supply pump side.
Accordingly, there is a need for an improved fluid power diaphragm pump which the stroke length of one or both of the diaphragm chambers can be easily modified. Further, there is a need for an improved fluid powered diaphragm pump where the stroke length can be modified during operation of the pump. Still further, there is a need for a fluid powered diaphragm pump whereby the stroke length of one or more of the diaphragm chambers can be modified without disassembly of the pump.